It is well known that soft water is more effective than hard water in washing clothes, dishes or other articles. To solve the problem of hard water, small water softeners associated with either a washing machine or a dishwasher have been used to soften the water entering the machine
In water softeners a decalcifier which may comprise a resin container exchanges both the calcium ions (Ca2+) and magnesium ions (Mg2+) contained in the water with sodium ions (Na+) contained in appropriate resins placed in the resin container. The resins are tiny beads, generally of an inert polymer structure.
Resins or other similar substances become exhausted after a certain usage time. Their ions Na+ to be exchanged with Ca2+ and Mg2+ contained in the water are consumed; as a result, water will still flow through the resin container but the hardness of the water is not reduced. This drawback is prevented through a resin regeneration cycle. A brine solution (NaCl) is introduced with the aim of regenerating the resin.
To adjust for different levels of water hardness EP219704 Milocco et al and EP433676 Bongini describe means for adjusting the mean path flow of the water through the resin container to adjust the level of water softening. Such arrangements are not easy to use and difficult to manufacture.
A difficulty as to when to replenish salt is addressed by EP0351564 Jerg et al using a mechanical float to indicate the presence or absence of salt. Mechanical float devices can stick and can give a wrong indication resulting in the presence of salt being indicated when there is a lack of salt and the water entering the washing appliance is consequently not soft enough.
Water softeners aim to keep the softness of water within desired bounds, in order to achieve this desire the resins in the resin container need to be kept charged with sodium ions (Na+). EP900765 Zucholl uses electrical conductivity sensors to detect the need to regenerate the resins. EP919178 Carli and EP1048776 Carli also use sensors to detect the degree of exhaustion of the resins. Such sensors include the physical volume of the resins, the pressure exerted by the resins on a switch and the movement of an element contained within the resin container. Such devices add complexity to manufacturing water softeners.
Controlling the volume of brine flushed through the resin container can also control the water softness. EP0367062 Fontana; EP545127 Milocco and EP0860140 Carli use water chambers to regulate the amount of brine flushed through the resins. The use of multiple water chambers adds to the difficulty of manufacturing such water softeners and adjusting such devices.